"The science of prevention and screening has changed," says John Santa, MD, MPH, director of the Consumer Reports Health Ratings Center. He oversaw the project.

"Consumers need to know that some screening tests are terrific, some are not good, and some can harm you," Santa says.

"We are not talking about people at high risk," he says. "And of course they are not symptomatic. We're not talking about what you should do if you have a mole that is changing or if you feel a breast lump."

The full report is in the March issue of Consumer Reports.

Cancer Screening: CR Ratings

To develop the ratings, Santa and his team looked at medical research, consulted medical experts, surveyed more than 10,000 readers, and talked with patients about screening tests.

They looked closely at recommendations of the U.S. Preventive Services Task Force. This independent panel provides guidelines on health care based on evidence. Much of Consumer Reports' recommendations follow the task force guidelines to the letter. But, their recommendations sometimes differ from those of organizations such as the American Cancer Society (ACS). Here, details on the three recommended tests:

Cervical cancer. Women 21 to 30 should have a Pap smear to test for cervical cancer every three years. Women 30 to 65 can wait five years if they have had testing for human papillomavirus (HPV), the virus that causes the cancer. Those 65-plus can skip screening if they were screened regularly earlier. Those under 21 can also skip the test, as experts know the cancer is not common at those ages.

Colon cancer. Those 50 to 75 should get screened regularly, and older people should discuss the pros and cons with their doctor and decide. Options include a colonoscopy, which examines the entire colon, every 10 years, or a sigmoidoscopy, which looks at the lower third, every five years plus a stool test every three years, or an annual stool test. As far as other guidelines, no groups suggest screening younger than 50 unless high risk. The ACS also doesn't say to specifically stop at age 75.

Breast cancer. Women 50 to 75 need a mammogram every two years. Those 40 to 49 or 75 andolder should talk with their doctor about pros and cons. These guidelines do split with those of the ACS, though. The cancer society recommends yearly mammograms after age 40 and as long as healthy.

The other eight tests were not recommended for those not at high risk because the cancers are uncommon, the test's effectiveness is not proven, or the test can't detect the disease at a curable stage. And even though some of the tests aren't really recommended by anyone, this list is a valuable reminder for people who may feel they need to seek them out.

On the "avoid" list, screenings for:

Bladder cancer. The test looks for blood or cancer cells in the urine.

Lung cancer. The test is a low-dose CT scan. The ACS only recommends this for high-risk people (such as older individuals who've smoked for years).

Skin cancer. The test is a visual exam of your skin to spot signs of the deadly skin cancer melanoma. The ACS says a skin exam by a doctor should be included as part of the routine check-up.

Oral cancer. This visual exam of the mouth is done by a dentist or other health care professional. The ACS suggests this as part of your normal routine oral care.

Prostate cancer. The blood test is known as the PSA (prostate-specific antigen) test. The ACS says to discuss PSA tests with your doctor, but doesn't recommend widespread screening of everyone.

Ovarian cancer. Tests include a blood test to look for a protein linked with the cancer, and a transvaginal ultrasound. This test is generally not recommended by anyone for the general public.

Pancreatic cancer. Tests are abdominal images or genetic tests. This test is also generally not recommended by anyone for the general public.

Testicular cancer. The test is a physical exam of the testicles. ACS does recommend this as part of routine care; the task force doesn't.

Cancer Tests: Perspectives

The new ratings drew mixed reactions.

Otis Brawley, MD, chief medical officer of the American Cancer Society, says the report helps to put screening into its proper perspective. "There has been a significant amount of over-promising and over-promoting," he says.

He frowns on aggressive campaigns that have included mammogram parties or group colonoscopies.

"A lot of screening is being done by organizations that can profit from it," he says.

"The truth is, certain tests do have some significant benefit, and every test has some limitations," he says. "In the spirit of informed decision-making, people need to understand both the potential for benefit and the potential for harm."

As mentioned, the recommendations on breast cancer screening from Consumer Reports and the American Cancer Society are different, but Brawley calls these differences ''minimal."

"We recommend women in their 40s get a mammogram on an annual basis, but we also recommend those women get information on the limitations," he says.

These include missing some cancers and ordering additional tests when no cancer turns out to be there.

Some doctors took issue with the decision to use the task force recommendations as the basic source.

"I'm disappointed they followed the task force guidelines, because we feel they are inadequate to protect women," says Debra Monticciolo, MD, chair of the American College of Radiology's Quality and Safety Commission and vice chair of radiology at Scott & White Healthcare in Temple, Texas.

"Right now, we can't cure breast cancer, so we really need to find cancers early," she says. Research has found the best way to do that is by yearly mammograms beginning at age 40, she says.

The recommendation to avoid PSA tests refutes evidence that they work, say Dipen Parekh, MD, a professor and chair of urology at the University of Miami Miller School of Medicine's Sylvester Comprehensive Cancer Center.

"There is no question the decline in the incidence of advanced prostate cancer is due in large part to PSA screening," he says.

However, the recommendation for women at low risk for ovarian cancer not to seek screening is a good one, says J. Matt Pearson, MD, assistant professor and a gynecologic oncologist at the University of Miami Miller School of Medicine's Sylvester Comprehensive Cancer Center.

The lifetime risk of ovarian cancer in the general population is low. When you screen for a cancer that is not common, he tells women, "you are more likely to find a benign abnormality that pushes you toward [unneeded] surgery."

Cancer Tests: Making the Decision

Santa recommends educating yourself about cancer screening tests, then talking to your doctor about whether the benefits outweigh the risks for you.

"Don't go to a mobile van, don't go to a mammogram party," he says.

"Don't believe a billboard on the highway that tells you to get a PSA test when it comes from a hospital that has a robotic prostate cancer surgery program."

Cancer Prevention: Lifestyle, Lifestyle, Lifestyle

"If you are serious about preventing cancer, you don't smoke, you exercise, and you try to get to a normal weight," Santa says. Obesity has been linked with about 4% of men's new cancers and 7% of women's, he says.

Getting to a normal weight may especially lower the risk for uterine and esophageal cancers.

Regular exercise can reduce colon and breast cancer risk.

Smoking is linked with lung cancer as well as cancers of the larynx, oral cavity, esophagus, bladder, kidney, and pancreas.